Azure Front Door 对orgin进行健康检测，通过http或https端口检测orgin是否健康。
Azure Front Door 只接受http response code 200为健康状态，其余response code均为不健康。
有些用户的heatlh probe response code 为403，会有多重情况造成这样的回复。
很多情况下用户可能对client ip设置了restriction。当Azure Front Door 的health probe IP 访问orgin时会被禁止访问，因此收到 403的response code。
那么Azure Front Door health probe 的source IP地址范围时什么呢？
可以从Azure service tag中找到source IP的地址范围。
通过这个链接下载Azure public service tag。
Download Azure IP Ranges and Service Tags -- Public Cloud from Official Microsoft Download Center
在下载的JSON文件中找到 AzureFrontDoor.Backend 这个service tag, 其中包含的IP地址就是Azure Front Door 用来进行health probe 的IP地址范围。
"name": "AzureFrontDoor.Backend",
"id": "AzureFrontDoor.Backend",
"properties": {
"changeNumber": 17,
"region": "",
"regionId": 0,
"platform": "Azure",
"systemService": "",
"addressPrefixes": [
"4.232.98.120/29",
"13.73.248.16/29",
"20.17.126.64/29",
"20.21.37.40/29",
"20.36.120.104/29",
"20.37.64.104/29",
"20.37.156.120/29",
"20.37.195.0/29",
"20.37.224.104/29",
"20.38.84.72/29",
"20.38.136.104/29",
"20.39.11.8/29",
"20.41.4.88/29",
"20.41.64.120/29",
"20.41.192.104/29",
"20.42.4.120/29",
"20.42.129.152/29",
"20.42.224.104/29",
"20.43.41.136/29",
"20.43.65.128/29",
"20.43.130.80/29",
"20.45.112.104/29",
"20.45.192.104/29",
"20.59.103.64/29",
"20.72.18.248/29",
"20.79.107.152/29",
"20.88.157.176/29",
"20.90.132.152/29",
"20.113.254.88/29",
"20.115.247.64/29",
"20.118.195.128/29",
"20.119.155.128/29",
"20.150.160.96/29",
"20.189.106.112/29",
"20.192.161.104/29",
"20.192.225.48/29",
"20.210.70.64/30",
"20.215.4.240/29",
"20.217.44.240/29",
"40.67.48.104/29",
"40.74.30.72/29",
"40.80.56.104/29",
"40.80.168.104/29",
"40.80.184.120/29",
"40.82.248.248/29",
"40.89.16.104/29",
"51.12.41.8/29",
"51.12.193.8/29",
"51.53.30.144/29",
"51.104.25.128/29",
"51.105.80.104/29",
"51.105.88.104/29",
"51.107.48.104/29",
"51.107.144.104/29",
"51.120.40.104/29",
"51.120.224.104/29",
"51.137.160.112/29",
"51.143.192.104/29",
"52.136.48.104/29",
"52.140.104.104/29",
"52.150.136.120/29",
"52.159.71.160/29",
"52.228.80.120/29",
"68.221.93.128/29",
"102.133.56.88/29",
"102.133.216.88/29",
"147.243.0.0/16",
"158.23.108.56/29",
"172.204.165.112/29",
"191.233.9.120/29",
"191.235.225.128/29",